Thermomotive device



Fig.4

A ril 23, 1946. vQ L HALL 2,399,020

THERMOMOTIVE DEVICE Filed Jan. 30, 1943 Inventor; Chesterlhal I,

His Attorney Patented Apr. '23, 1946 f THERMOMOTIVE DEVICE Chester I.Hall, Vischers Ferry, N. Y., assignor to General Electric New YorkCompany, a corporation of Application January 30, 1943, Serial No.474,210

11 Claims. (01. 137-139) The invention relates to thermomotive devices,particularly valves operated by an electrically heated thermomotiveelement, and the principal object is to provide an improved form ofadjustable range thermomotive operating mechanism employing anelectrically heated extensible element for operating valves or otherdevices.

Various forms of electrically heated thermomo tlve operating mechanismshave been proposed,

as such a mechanism can be made absolutely quiet and therefore is betteradapted for alternating current energization than the conventionalsolenoid. Also, the force developed by an electrically heatedthermomotive operating element can be made relatively large compared toa solenoid of equal electrical rating so as to, insure greaterreliability. Furthermore, a thermomotive mechanism inherently can openand close a valve or operate other devices more slowly than a solenoidwhich is of material advantage in some service as, for example, inavoiding water hammer or in gradually controlling gas fired heatingequipment. In addition, a thermomotive mechanism may be made to operateequally well in any position.

However, since solenoids still remain predominant in common use foroperating valves and other devices, the various forms of electricallyheated thermomotive operating mechanisms heretofore proposed still leavesomething to be desired.

One of the objects of the present invention is to provide an improvedthermomotive operating mechanism having cooperating range adjustingmeans connected with the opposite ends of a relatively quick heating andcooling current conducting tension wire or strip for jointly controllingthe heating and cooling time delays involved in the operation of thevalve or other control relatively wide heating and cooling range so asto reduce the active length thereof and to be adjustably mounted underadjustable tension at ambient temperature substantially parallel withand adjacent to the valve diaphragm operated thereby. This not onlyenables a more compact and practical valve structure to be obtained withthe operating parts thereof readily accessible for. adjustment, repair,or replacement, ,but also overcomes many of the usual difficulties thatare encountered in extensibly mounting, housing, heating, cooling, andoperatively connecting a ther- 'momotive valve operating element.

A further object is to enable the pressure of the controlled fluid onthe diaphragm valve to be utilized to open the valve with or without aninitial snap action when the thermomotive element is heated according tothe adjustment of the thermomotive operating mechanism while theincreased tension produced upon cooling of the thermomotive wire orstrip correspondingly serves to close the diaphragm valve with orwithout a final snap action.

A special object is to provide the improved adjustable rangethermomotive operating mechanism with a variable lost motion springhaving a preadjustable strainrelease stop for regulating the operatingtemperature range of an electrically heated thermomotive wire or stripso as thereby tocontrol the operating time.

The preadjustable variable lost motion range adjusting spring strainrelease stop enables the improved mechanism to effect the "operatingmovements of the valve or other device operated thereby while thetemperature of the thermomoybient temperature or is heated to itsmaximum temperature.

Further objects and advantages of the invention will appear in the.iollowlng description of ,the accompanying drawing in which Fig. 1 is asectional view of a thermomotive diaphragm valve embodying the inventionin a preferred form; Fig. 2 is a top view of the thermomotive valvestructure shown in Fig. 1; Fig. 3 is an enlarged view showing moreclearly the mounting and energizing connections for the thermomotiveextensible wire or strip; and Fig. 4 is a schematic diagram showing theimproved valve connected to control the operation of a gas 'burner underthermostatic control.

As shown in Fig. 1, the diaphragm valve body 10 is provided with acylindrical valve seat H for cooperating with the flexible valvediaphragm l2 to control the flow of fluid from the inlet opening Hi tothe outlet opening M. The flexible diaphrasm 12 carries the stiffeningplates 15 and I6 on the opposite sides thereof for mounting theoperating pm I! having the rounded head I8 by the holding-down screws2!.

The removable clamping plate is provided with a pair of mounting yokes22 and 28 for pivotaliy supporting the movable adjusting brackets 24 and25 on the pins 28 and 21 so that these brackets can adjustably carry theelectrical insulating tubes 28 and 29 on the pins 30 and 3|. Theseinsulators are provided with suitable central grooves for receiving themounting wire loops 32 and 33 that are connected to theends of thethermomotive tension element that operates the valve. In order toaccelerate the: heating and cooling thereof, the thermomotive tensionelement 40 is in the form of a very thin flat wire or strip with theends thereof folded over and brazed for mechanical reinforcement, asindicated more clearly in Fig. 3. The thermomotive strip 40 may beformed of nichrome or other suitable high resistancepurrent conductingmaterial that has a high tensile strength and a substantialcoefilcientof expansion and can successfully withstand operation at relatively hightemperatures for extended periods without deterioration.

As shown in Fig. 3, the mounting wire loop 33 extends freely through thehole 4i formed in the folded over end of the thermomotive element 40with the ends of the loop 83 joined together along with the end of theflexible ,lead 42 for the circult connection terminal 43, preferably bysilver brazing. The mounting of the other end of the thermomotiveelement 40 is accomplished in the same way. Thus the two terminals 43for conducting the heating current to the thermomotive element to may bemounted on a suitably insulated terminal block 45 with sufficientflexibility in the leads 42 to permit relatively free pivotal movementof both of the adjusting brackets 24 and 25.

The motion transmitting connections for the thermomotive element 40include a pivoted bracket 24 and the cooperating variable lost motionspring 5|. The pivoted bracket 24 is provided with an operating armextending substantially parallel with and between the strip do and thediaphragm l2. The variable lost motion range adjusting spring 5i issecured to arm 50 by the rivet'52 so that the free end thereof extendsinto biasing engagement with the rounded head l8 of the diaphragm valveoperating pin H. The arm 50 also carries the adjustable strain releasestop screw 53 for engaging with the free end of the biasing spring 5| soas to stop the release of the strain of this spring and thereby controlthe valve operating characteristics, particularly the operating time forthe diaphragm valve, as explained more in detail hereafter. When thedesired valve operating characteristic is obtained. the adjustablestrain release stopscrew 88 is locked in position by the nut 54.

The pivoted bracket 25 is provided with the arm 55 so that its angularposition may be adjusted by means of the adjusting screw 68 and the locknut 61 to place the thermomotive element 40 under a varying amount oftension at the normal ambient temperature to flex the biasing spring illa variable distance away from the strain release stop screw 53 when thediaphragm valve is in the closed position, as shown. In this way theself-heating, current conducting extensible thermomotive valveoperating'el'ement 40 is adjustably mounted under adjustable tensionsubstantially parallel with and adjacent to the diaphragm 12 of thevalve. Thus a suitably ventilated removable cover, indicated by thedotted lines 58, may be provided for engaging with the top plate 20 soas fully to enclose the thermomotive operating mechanism of the valvewhile providing ready access for adjustment, repair or replacement ofthe parts.

As shown in Fig. 4, the diaphragm valve i0 is connected to control theflow of gas from the supply pipe 60 to the gas burner iii. The burner BIis provided with the usual pilot igniter 82 supplied from the pipe 60through the pilot regulating valve 63. The thermomotive operatingelement 40 is connected to be supplied with heating current from thesecondary of a transformer 64. The primary of the transformer 84 isenergized from the supply lines Li, L2 through the conductors 65 and 66under the control of the relay 61 and the adjustable current regulatingresistor 68. The operating winding 89 of the relay in turn is energizedfrom the supply lines under the control of the thermostat 10 to controlthe operation of, the valve in in the following manner.

Operation When the thermostat 10 closes its contacts, the winding 59 isenergized to close the relay contact 61 and thereby energize the primaryoi. transformer 64. The transformer 64 supplies a relatively largecurrent at low voltage to effect a rapid heating of the thermomotivevalve operating element 4!), the amount of heating currentbeingcontrolled by the adjustment of resistor 68. As a result, both thetemperature and the length of the element 40 may be increased at arelatively rapid initial rate. As the length of element 40 increases,the strain of the biasing spring 6| rotates the arm 50 and the bracket24 in a clockwise direction about the pivot pin 26 while stillmaintaining the diaphragm valve l2 closed due to the lost motionprovided by the unflexing of spring 5i. Thus for a predetermined timeafter the thermomotive element 40 is energized, the arm 50 will berotating a predetermined amount dependent jointly upon the adjustmentsof the strain release stop 53 and of the tension adjusting screw 56before bringing the adjustable stop screw 53 into engagement with theend of the spring El. Thereupon the free end of the spring 6| will moveas a unit with the arm 50 to permit the gas pressure exerted on thediaphragm l2 over the limited area of the valve seat ii to effect aninitial opening of the valve.

In case the joint adjustments of screw 56 to control the initial tensionof the thermomotive element 40 at ambient temperature, and of the strainrelease stop screw 53 to control the lost motion of the thermomotivemechanism are such that the increased force exerted by the gas pressureover the entire area of the diaphragm l2 after the initial opening ofthe valve is insuihcient to flex the end of the spring 5| away from theadjustable stop 53, then the continued opening movement of the valvewill be proportional to the further increase in length of thethermomotive element 40 which may be varied by adjusting resistor 88 tovary the heating current supplied to the element. Thus the openingmovement of temperature.

opens its contacts to drop out the relay 8'! and 9,899,020 the diaphragmvalve 12 will gradually continue at a progressively decreasing rateuntil the thermomotive element 40 has been heated to-its maximumtemperature above the ambient at which the heat losses from the thincurrent conducting strip will equalize with the heat electricallygenerated therein.

In accordance with the present invention, the joint control of the lostmotion by the strain release stop screw 53 and the tension adjustingscrew 56 enables the temperature of the thermomotive element 40 to beincreased a predetermined amount above the ambient during an initialheating interval before the initial opening of the valve is eflected andthereby insures that the valve operating temperature range of thethermomotive element is well above the ambient.v

As a result, the valve is opened gradually during the subsequent heatinginterval required for the thermomotive element to reach its maximumThus, when the thermostat 10 thereby deenergize the thermomotive element40; the cooling of the thermomotive element 40 from its maximumtemperature will occur at a rela-" tively rapid initial rate whichprogressively decreases as the ambient is approached. The resultingrelatively rapid decrease in the length of thermomotive element 60 willefi'ect the closing movement of the diaphragm valve l2 at acorrespondingly rapid rate since the final closing of the valve will beeffected while the temperature of the thermomotive element 46 is stillwell above the ambient. may, if desired, be made relatively short.

By suitably adjusting the stop screw 53 and adjusting screw 58, thetotal time required after closure and opening of the contacts ofthermostat 10 for correspondingly opening and closing the valve l2 maybe substantially equalized or, if desired, a relative variation of thevalve opening and closing time may be obtained. Thus, adjusting toincrease the initial tension of element 40 or to increase the lostmotion of the stop screw 53 so as to increase the rise intmperature ofthe thermomotive element 40 above ambient required to initiate openingof .the valve will serve to decrease the valve closing time relative tothe valve opening time, while oppositely'adjusting to decrease thetemperature rise of the thermomotive element 40 above ambient requiredto initiate opening of the valve will accomplish theopposite results.Likewise, if desired, the joint adjustments of the lost motion stopscrew 53 and the tension adjusting screw 56 may be made for the purposeof varying the amount of opening of valve l2 obtained when the maximumrise in temperature of element 40 occurs. Thus by adjusting screw 56 toincrease the initial tension of element 50 and at the same timeadjusting screw 53 to increase the lost motion, then the total amount Inthis way the valve closing time,

pressure exerted over the total area of the dia- Dhragm I2 upon theinitial opening of the valve will become suflicient to flex the end ofthe spring 5| away. from the stop 53. In this way, a limited snap actionof the diaphragm I? will be effected upon each initial opening of thevalve. Similarly with such adjustment when the valve is almost closed,the resulting reduction in gas pressure over the total area of thediaphragm l2 will enable the strain in the flexed spring 5| topredominate and thereby eflect a limited snap action in the finalclosing of the valve.

Thus the improved thermomotive operating mechanism of the presentinvention enables various combinations of selective adjustments to bemade to meet many widely varying heating and cooling time as well asother service requirements in valve operating or other control service.Furthermore, all theoperating parts are readily accessible foradjustment, repair, or replacement since in the preferred formillustrated the removable valve diaphragm clamping plate 20 carries theentire thermomotive operating mechanism.

What I claim as new and desire to secure by Letters Patent of theUnitedStates is:

1. In combination, a diaphragm valve subject to fluid pressure forbiasing said valve open and having a removable diaphragm clamping plateprovided with a pair of pivoted brackets, each having an insulatorcarried thereby, a self heating current conducting thermomotive tensionstrip having mounting means at the ends thereof for engaging saidinsulators, a valve operating arm extending from one of said bracketsand provided with a biasing spring for operatively engaging saiddiaphragm valve to effect closure thereof and having an adjustable stopcarried thereby for engaging said spring to control the release of thestrain thereof in opening said valve and means for adjusting the otherof said brackets i to place said strip under tension sufilcient to movesaid spring away from said stop with said strip at ambient temperatureto inversely vary the heating interval of said strip required beforeopening said valve and the cooling interval of said strip required forclosing said valve.

2. In combination, a valve biased open, a thermomotive operatingmechanism for closing said of opening of valve l2 when the maximum risein limit of the diaphragm itself. Furthermore, in case it should bedesired to obtain an initial snap action in the opening of the valve anda flnal snap action in the closure thereof, adjustment of the tensionof'spring Si by the strain release stop screw 53 and the tensionadjusting screw 58 may be made so that the gas valve including aself-heating current conducting thermomotive tension strip havingadjustable mounting means at one end thereof, and a valve operating armoperated by the other end of said strip and provided with a biasingspring for operatively engaging said valve to effect closure thereof andan adjustable strain release stop for said spring to control the valveclosing temperature of said strip andthereby inversely varying thecooling interval 01 said strip required for closing said valve and theheating interval of said ,strip required before opening said valve.

3. In combination, a movable member having a predetermined limit ofmotion in one direction and biasing means for effecting movement thereofin the opposite direction, a relatively movable member having a springfor moving said first member in said one direction and provided with anadjustable stop movable as a unit with said relatively movable memberfor controlling the release of the strain 01 said spring, and operatingmeans including an electrically heated thermomotive element for movingsaid relatively movable member to operate said first member uponvariation of the temperature of said element within a range variableupon the adjustment of said stop to relatively vary the heating andcooling time delay 0! said element in said range.

4. In combination, a movable control element having a motion limitingposition, means for biasing said element to move from said limitingposition to other positions, an operating member having a relativelymovable spring for predominating over said biasing means and providedwith an adjustable strain release stop, and an electrically heatedthermomotive tension element having a tension adjusting mounting meansat one end thereof and having the other end thereof connected with saidoperating member for moving said spring and said stop to return saidcontrol element to said limiting position at the end oian interval ofcooling of said thermomotive element predetermined jointly by theadjustment of said strain release stop and the adjustment of saidtension adjusting mounting means.

5. In combination, a movable control element having a motion limitingposition, means for biasing said element to move from said limitingposition to other positions, means including a movable spring foropposing said biasing means and provided with an adjustable strainrelease stop movable as a unit with said spring, and an electricallyheated thermomotive tension element for moving said spring and said stopto return said control element to said limiting position at the end ofan interval of cooling of said thermomotive element variable by theadjustment of said stop.

6. In-combination, a movable control element having a motion limitingposition, means for bias ing said element to move from said limitingposition to a variable position, a movable spring for opposing saidbiasing means and provided with an adjustable strain release stopmovable as a unit with said spring, and an electrically heatedthermomotive tension element ior. moving said spring and said stop toreversely operate said control element between said positions in heatingand cooling intervals relatively variable by the adjustment of saidstrain release stop.

7. In combination, 'a movable control element, means for biasing saidelement to move from a predetermined control position, and meansincluding a current conducting thermomotive tension strip having amovable spring strained thereby ior holding said element in saidposition and provided with an adjustable strain release stop foreffecting movement of said control element from said position after theelectrical heating of said strip for an interval variable by theadjustment or said strain release stop.

8. A variable time delay load operating mechanism having. incombination, an electrically heated thermomotive element, a movable loadmember having a predetermined limit of motion and provided with meansfor biasing said member to move therefrom, means including a springcontrolled by said element for moving said member to said limit at theend of an initial interval of cooling of said element and maintainingsaid member at said limit during the subsequent cooling interval of saidelement, and said spring having an adjustable resiliency stop forinversely varying said intervals.

9. In combination, a thermomotive operating element having heatingmeans, motion transmitting connections for said element including a lostmotion spring, and means for varying the lost motion of said springincluding an adjustable stop for variably limiting the unfiexing of saidspring.

10. In combination, a thermomotive element having heating means, motiontransmitting connections for said element including a lost motion springfor unilexing to provide lost motion in the initial part of the heatingrange of said element and means for varying said lost motion part ofsaid range including an adjustable stop carried by one of saidconnectionsior variably limitingv the unfiexing of said spring.

11. In combination. a thermomotive operating element, means for varyingthe temperature of said element at progressively decreasing rates duringboth heating and cooling, a motion transmitting-member connected withsaid element and having a motion transmitting spring movable to apredetermined limit of motion transmission as a unit with said memberupon cooling of said element and flexible relative to said member toprovide lost motion after said limit is reached, means for adjustingsaid element to vary the flexure of said spring relative to said memberwhen said element is cool, and means including an adjustable stopcarried by said member for variably limiting the unflexing of saidspring to inversely vary the rates of heating and cooling motion 0! saidelement transmitted by said spring adjacent said limit.

CHESTER I. HALL.

